1. Field of the Invention
The present invention relates to an electric power or electric energy conversion/storage system and an electric energy converting/storing method for generating or producing an ozone gas by using electric energy and storing the ozone gas for supplying it to an ozone utilization object (hereinafter referred to as ozone consumer) continuously at a given flow rate, as occasions demand.
2. Description of Related Art
For having better understanding of the invention, technical background thereof will first be described. Heretofore, as the electric energy storage apparatuses for storing electric energy generated during the night, there are well known in the art the apparatuses designed for converting the electric energy into heat for storing the former in the form of thermal energy, as exemplified by an electric water heater, a heat-accumulation type hot-air generator, a cold-accumulation type cooler and the like. FIG. 18 is a side elevational view showing in section a structure of a conventional electric energy conversion/storage system such as an electric water heater. Referring to the figure, the electric energy conversion/storage system includes a hot-water inlet port 1 mounted at the top end, and a heat insulator 2 serving for preventing hot water as poured through the hot-water inlet port 1 from getting cool.
Formed integrally in the heat insulator 2 is a hot water reserving tank 3 in which an electric heater 4 is disposed for heating water stored in the hot water reserving tank 3 as occasion demands. The temperature of hot water contained within the hot water reserving tank 3 is detected by a temperature sensor 5, wherein the temperature detection signal outputted from the temperature sensor 5 is supplied to an automatic temperature regulating unit 6 which serves to control or adjust the temperature of hot water within the hot water reserving tank 3. Hot water stored within the hot water reserving tank 3 can be taken out through a water outlet port 7 mounted at a location close to the bottom of the electric water heater.
Operation of the conventional electric energy conversion/storage system (electric water heater) shown in FIG. 18 will be briefly reviewed below.
When water is fed to within the hot water reserving tank 3 through the water inlet port 7, water is heated up to a predetermined temperature and taken out as hot water through the hot-water outlet port 7, as it is demanded. The temperature of hot water contained within the hot water reserving tank 3 is detected by the temperature sensor 5 disposed within the hot water reserving tank 3. The electric power supply to the temperature sensor 5 is controlled by means of the automatic temperature regulating unit 6 so that the temperature of the hot water contained within the hot water reserving tank 3 is maintained at a value preset at the automatic temperature regulating unit 6. In this manner, in the electric water heater now under consideration, electric energy is transformed into heat or thermal energy and stored in water which may thus be referred to as a heat storing or accumulating medium.
Further, FIG. 19 is a side elevational view showing in section a heat-accumulation type hot-air generator as another one of the conventional electric energy conversion/storage systems known heretofore. In the figure, reference numeral 4 and 6 designates an electric heater and an automatic temperature regulating unit described above in conjunction with FIG. 18. The heat-accumulation type hot-air (or gas) generator includes a thermal insulation layer 8 for suppressing heat as stored from dissipating to the ambient, and a heat accumulating medium 9 charged within a chamber enclosed by the thermal insulation layer 8. An air flow passage 10 extends through the heat accumulating medium 9 for allowing air flowing through the passage 10 to take out heat from the heat accumulating medium 9. Further provided is a blower 11 which serves for feeding air into the passage 10. In the heat-accumulation type hot-air generator described above, there is usually employed as the heat accumulating medium 9 a heat resistant brick or the like material.
Operation of the heat-accumulation type hot-air generator shown in FIG. 19 will be described below. The heat accumulating medium 9 charged within the chamber defined by the thermal insulation layer 8 is heated by the electric heater 4 up to a value preset at the automatic temperature regulating unit 6. Thus, electric energy is converted or transformed into heat or thermal energy to be stored in the heat accumulating medium 9. Heat accumulated in this manner can be extracted by air which is forced to flow through the passage 10 by means of the blower 11 with heat transfer taking place between the heat accumulating medium 9 and the air flow known heretofore.
Further, FIG. 20 is a schematic diagram showing a general arrangement of a conventional intermittent-operation type ozone supply system which represents another example of the electric energy conversion/storage system.
Referring to FIG. 20, a raw material gas (hereinafter referred to as the raw gas) containing oxygen (i.e., oxygen containing gas) fed from an oxygen supplying source 13 undergoes ozonization under the action of electric discharge (not shown) within an ozone generator (which is also referred to as the ozonizer) 12. To this end, a circulating blower 14 is provided for circulating the oxygen containing gas supplied from the oxygen supplying source 13 to a gas circulation system including the ozone generator 12.
Further provided is an ozone adsorption/desorption tower 15 serving as an ozone adsorption/desorption means for adsorbing ozone molecules from the ozonized gas (ozone containing oxygen gas) and desorbing ozone from the adsorbed state. The ozone adsorption/desorption tower 15 is charged with an adsorbent (described later on) for storing temporarily ozone molecules contained in the gas fed from the ozone generator 12. Further provided in the ozone supply system are a coolant supply source 16 for supplying a coolant for cooling the ozone adsorption/desorption tower 15, a heating medium source 17 for supplying a medium for heating the ozone adsorption/desorption tower 15 and a water ejector 18 for extracting or desorbing ozone molecules under depressurization from the ozone adsorption/desorption tower 15.
The adsorption/desorption tower 15 is implemented in a double-drum or double-cylinder structure, wherein the inner drum or cylinder 15a is filled with an adsorbent while the outer drum or cylinder 15b is filled with a heat transfer medium. Parenthetically, silica gel is commonly used as the adsorbent with ethylene glycol or alcohols being used as the heat transfer medium, wherein the inner cylinder 15a is fluidally communicated with the ozone generator 12, the circulating blower 14 and the water ejector 18, while the outer cylinder 15b is communicated with the coolant supply source 16 and the heating medium source 17.
Further, a variety of change-over valves 19a to 19g are interposed between exit ports and inlet ports of the ozone adsorption/desorption tower 15. More specifically, the change-over valves 19a and 19b are installed at locations upstream and downstream, respectively, of the coolant supply source 16, the change-over valves 19-c and 19d are installed between the ozone adsorption/desorption tower 15 and the circulating blower 14 and between the ozone adsorption/desorption tower 15 and the ozone generator 12, respectively, the change-over valve 19-e is installed at a connecting point or a junction between the ozone adsorption/desorption tower 15 and the water ejector 18, and the change-over valves 19-f and 19g are installed at locations upstream and downstream, respectively, of the heating medium source 17.
Next, description will turn to operation of the conventional intermittent-operation type ozone supply system shown in FIG. 20.
At first, in an ozone adsorption operation mode, an oxygen gas is supplied from the oxygen supplying source 13, whereby the gas circulation system including the ozone generator 12 and the circulating blower 14 is maintained constantly at a predetermined pressure. In practical applications, this pressure is usually set at 1.5 kg/cm2.
When the oxygen gas is forced to flow through the gas circulation system by driving the circulating blower 14 with the change-over valves 19c and 19d being opened, a part of the oxygen gas is transformed into ozone (i.e., ozonized) under the effect of silent electric discharge when the oxygen gas flows through an electric discharge gap defined between electrodes (not shown) disposed within the ozone generator 12, whereby an ozonized oxygen gas (i.e., ozone containing oxygen gas) is produced to be subsequently transported to the adsorption/desorption tower 15. The amount of oxygen consumed in producing ozone during this process is supplemented from the oxygen supplying source 13.
The adsorbent charged in the ozone adsorption/desorption tower 15 adsorbs selectively ozone molecules from the ozonized oxygen gas, wherein a residual part of the oxygen gas is fed back toward the circulating blower 14 through the change-over valve 19c. In this connection, the ozone adsorbent has such a property that the ozone adsorption capacity increases as the temperature thereof becomes lower. In consideration of this fact, the cooling temperature of the ozone adsorption/desorption tower 15 is usually maintained at a level not higher than xe2x88x9230xc2x0 C. by means of the coolant supply source 16.
When the ozone adsorbent reaches a saturated adsorption level, operation of the ozone storage/supply system is changed over to an ozone desorbing operation mode. In this case, operations of the ozone generator 12, the circulating blower 14 and the coolant supply source 16 are stopped with the change-over valves 19a, 19b, 19c and 19d being closed.
Subsequently, the heating medium source 17 and the water ejector 18 are put into operation with the change-over valves 19e, 19f and 19g being opened. In this case, the heating medium source 17 serves to increase the temperature of the adsorbent by applying heat for the purpose of facilitating or promoting the desorption of ozone molecules from the adsorbent.
Ozone molecules desorbed from the adsorbent filled in the ozone adsorption/desorption tower 15 are drawn or drained into the water ejector 18 under the effect of depressurization prevailing at the exit side of the ozone adsorption/desorption tower 15 to be thereby dispersed and solved in water. Ozone containing water thus produced is then carried to a utilization facility, i.e., ozone consumer.
The conventional electric energy storage methods and apparatuses suffer various shortages. In the case of the heat storage apparatus shown in FIGS. 18 and 19, the amount of heat which can be stored per unit volume of the heat storing medium is determined previously. Accordingly, an attempt for increasing the amount of electric energy which can be stored or accumulated will naturally be accompanied with a correspondingly increased volume of the heat storing/accumulating medium. Thus, the conventional apparatus can not satisfactorily meet the demand, i.e., lacks in adaptability required in practical applications.
Besides, the heat storing capability of the apparatuses as well as demand for the thermal energy is not constant throughout the year but undergoes variations in dependence on environmental temperature and the seasons, giving rise to a problem that the electric energy can not be stored for subsequent utilization with high efficiency.
On the other hand, in the case of the intermittent-operation type ozone supply apparatus shown in FIG. 20, there is a problem that the ozone gas can not be supplied to the ozone consumer steadily at a predetermined flow rate. Besides, because water is used for taking out ozone molecules, utilization of ozone is limited to water treatment applications. Additionally, since ozone is easy to decompose within water (decomposition occurs within a few minutes), limitation is imposed on the time or period for utilizing ozone.
In the light of the state of the art described above, it is an object of the present invention to provide an electric power converting/storing method which is capable of storing ozone generated by using electric energy with high efficiency.
Another object of the present invention is to provide an electric energy conversion/storage system which is capable of storing ozone produced by using electric energy and which allows ozone as stored to be supplied steadily at a predetermined flow rate to an ozone consumer as occasion demands it.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to an aspect of the present invention an electric energy converting/storing method which includes the steps of producing an ozonized gas by using electric energy during a time period in which electric power consumption is low, storing ozone contained in the ozonized gas, and taking out the stored ozone as an ozone containing gas for utilization thereof during a time period in which the electric power consumption is high.
With the method described above, demand for the electric energy can be uniformized throughout the day and the night owing to the effective utilization of the electric energy during the night in which the demand for the electric energy is low.
In a preferred mode for carrying out the method mentioned just above, the ozonized gas may be compressed for storage in the zone storing step.
With the method mentioned just above, electric energy can be stored with an enhanced efficiency because the ozone gas produced by utilizing electric energy is stored in the compressed state. Besides, utilization of electric energy can be uniformized. Additionally, ozone storage and discharge operation can be much facilitated by storing the ozone gas in the compressed state.
In another preferred mode for carrying out the method mentioned above, ozone concentration of the ozonized gas upon storage thereof in the compressed state may be set in a range of 10xc2x13% by weight.
With the method mentioned above, the ozone gas can be stored with electric energy utilization efficiency while protecting ozone molecules from being decomposed upon storage thereof.
In yet another preferred mode for carrying out the method mentioned previously, ozone contained in the ozonized gas may be absorbed by a solvent for storage thereof.
Owing to the use of a solvent as mentioned above, storage of ozone gas as well as delivery thereof can be much facilitated.
In still another preferred mode for carrying out the method described just above, the solvent should preferably be an organic solvent.
In this case, the amount of ozone molecules as adsorbed per unit volume of adsorbent can be significantly increased, which of course contributes to more effective utilization of electric energy.
In a further preferred mode for carrying out the method mentioned previously, ozone contained in the ozonized gas may be adsorbed by an adsorbent for storage thereof.
Owing to the use of adsorbent for the storage of ozone gas, not only the ozone storage but also delivery of the ozone gas can be much facilitated, which of course contributes to uniformization of the electric energy demand.
In a yet further preferred mode for carrying out the method mentioned just above, the adsorbent may be comprised of at least one selected from a group consisting of a porous material impregnated with fluorocarbon, silica gel, activated alumina and combinations thereof.
With the adsorbent formed of the material mentioned above, decomposition of ozone molecules upon storage of the ozone gas can be suppressed to a minimum, ensuring effective utilization of electric energy.
According to another general aspect of the present invention, there is provided an electric energy conversion/storage system which includes an ozone generating means for producing an ozonized gas from a raw material gas containing oxygen by utilizing electric energy, an ozone adsorbing/desorbing means for adsorbing ozone contained in the ozonized gas and desorbing ozone adsorbed, a gas circulation system for causing the raw material gas and the ozonized gas to flow by way of the ozone generating means and the ozone absorbing/desorbing means while feeding back to the ozone generating means a residual oxygen gas remaining after adsorption of ozone from the ozonized gas, a coolant supply means for cooling the ozone adsorbing/desorbing means, and an ozone discharging means for taking out an ozone containing gas which contains ozone from the ozone adsorbing/desorbing means to thereby supply the ozone containing gas to an ozone consumer. The ozone discharging means includes an ozone concentration control means for enabling supply of the ozone containing gas to the ozone consumer substantially at a predetermined ozone concentration and substantially at a predetermined constant flow rate.
With the arrangement of the electric energy conversion/storage system described above, the ozone molecules can be stored efficiently while ozone gas can steadily be supplied to the ozone consumer at a predetermined ozone concentration and at a predetermined flow rate. Besides, storage and delivery of the ozone gas can be facilitated.
In a preferred mode for carrying out the invention, the electric energy conversion/storage system described just above may further include a pressure sustaining means for sustaining a pressure within the ozone adsorbing/desorbing means to be higher than the atmospheric pressure.
With the arrangement mentioned above, ozone adsorption capability of the adsorbent can be improved, whereby ozone storage efficiency as well as electric energy utilization efficiency of the electric energy conversion/storage system can be significantly enhanced.
In another preferred mode for carrying out the invention, the pressure sustaining means mentioned above may include a pressurizing pump means disposed at an entrance side of the ozone absorbing/desorbing means, a flow regulating means for adjusting a flow rate of the ozonized gas supplied to the pressurizing pump means to be substantially constant, and a back-pressure valve means disposed at an exit side of the ozone adsorbing/desorbing means for restoring pressure of the raw material gas supplied to the ozone generating means to the atmospheric pressure.
By virtue of the arrangement mentioned above, the ozonized oxygen can be supplied at high pressure only to the adsorption/desorption tower, which contributes to more effective ozone storage.
In yet another preferred mode for carrying out the invention, the electric energy conversion/storage system may further be so arranged as to include an inert gas supply means for supplying an inert gas to the gas circulation system.
Owing to the arrangement mentioned above, the electric discharge can easily take place even under a high pressure. Thus, ozone gas can be produced with high efficiency while assuring effective utilization of electric energy.
In still another preferred mode for carrying out the invention, an argon gas should preferably be selected as the inert gas.
By using argon gas as the inert gas, the amount of heat dissipated from the adsorbent upon ozone adsorption can be reduced, which in turn ensure utilization of electric energy with high efficiency with energy required for cooling the adsorbent being reduced.
In a further preferred mode for carrying out the invention, the ozone concentration control means mentioned previously may include an ozone densimeter for measuring an ozone concentration of the ozone containing gas, a first flow regulating valve for regulating a flow rate of the ozone containing gas taken out from the ozone adsorbing/desorbing means, a second flow regulating valve for regulating a flow rate of the ozone containing gas supplied to the ozone consumer, and a control means for controlling the first and second flow regulating valves on the basis of the ozone concentration. The control means may be so designed as to control the first and second flow regulating valves such that flow-path cross-sectional area of the first flow regulating valve is decreased while that of the second flow regulating valve is increased when the ozone concentration is higher than a predetermined ozone concentration. Further, the control means may be designed as to control the first and second flow regulating valves such that the flow-path cross-sectional area of the first flow regulating valve is increased while that of the second flow regulating valve is decreased when the ozone concentration is lower than the predetermined ozone concentration.
With the arrangement described above, ozone can be supplied to the ozone consumer steadily at a predetermined ozone flow rate.
In a yet further preferred mode for carrying out the invention, the ozone concentration control means may include an ozone densimeter for measuring an ozone concentration of the ozone containing gas, a depressurization regulating means for regulating depressurization required for taking out ozone from the ozone adsorbing/desorbing means, a flow regulating valve for regulating a flow rate of the ozone containing gas supplied to the ozone consumer, and a control means for controlling the depressurization regulating means and the flow regulating valve on the basis of the ozone concentration. The control means may be so designed as to control the depressurization regulating means and the flow regulating valve such that the depressurization is lowered while flow-path cross-sectional area of the flow regulating valve is increased when the ozone concentration is higher than a predetermined ozone concentration. Further, the control means may be so designed as to control the depressurization regulating means and the flow regulating valve such that the depressurization is intensified while the flow-path cross-sectional area of the flow regulating valve is decreased when the ozone concentration is lower than the predetermined ozone concentration.
With arrangement mentioned above, ozone can be delivered to the ozone consumer steadily at a predetermined flow rate.
In a still further preferred mode for carrying out the invention, the depressurization regulating means may include a gas ejector for extracting ozone from the ozone adsorbing/desorbing means by lowering the pressure within the ozone adsorbing/desorbing means, wherein the gas ejector may be comprised of a nozzle through which a compressed gas is caused to flow. The control means may be so designed as to control the depressurization by adjusting a diameter of the nozzle.
With the arrangement described above, ozone can be supplied to the ozone consumer stably by adjusting the nozzle diameter of the gas ejector.
In a further preferred mode for carrying out the invention, the depressurization regulating means may include a gas ejector for extracting ozone from the ozone adsorbing/desorbing means by lowering the pressure within the ozone adsorbing/desorbing means, a bypass pipe disposed in parallel with the gas ejector, and a two-way flow regulating valve for regulating a flow ratio of compressed gas flow between the gas ejector and the bypass pipe. The control means may be so designed as to control the depressurization within the ozone adsorbing/desorbing means by regulating the compressed gas flow ratio by controlling the two-way flow regulating valve.
With the arrangement described above, supply of the ozone gas to the ozone consumer can be carried out steadily.
In another preferred mode for carrying out the invention, the electric energy conversion/storage system may further include a gas storing means for storing a compressed gas to be used for driving the gas ejector.
By employing the gas storing means mentioned above, the electric energy required for taking out ozone from the ozone adsorption/desorption tower can be reduced, whereby ozone can be delivered to the ozone consumer with high efficiency.
In yet another preferred mode for carrying out the invention, the gas storing means may be composed of a compressed gas storing tank.
By using the gas storing means mentioned above, the electric energy required for taking out ozone from the ozone adsorption/desorption tower can be reduced, whereby ozone can be delivered to the ozone consumer with high efficiency.
In still another preferred mode for carrying out the invention, the gas storing means can be comprised of an air liquidizing means for storing air in a liquidized state.
By using the gas storing means as mentioned above, the electric energy required for taking out ozone from the ozone adsorption/desorption tower can be reduced, whereby ozone can be delivered to the ozone consumer with high efficiency.
In a further preferred mode for carrying out the invention mentioned previously, the air liquidizing means may be disposed in association with the ozone adsorbing/desorbing means so that the air liquidizing means serves additionally as a coolant supply source for the ozone adsorbing/desorbing means.
By employing the gas storing means as mentioned above, the electric energy required for taking out ozone from the ozone adsorption/desorption tower can be reduced, whereby ozone can be delivered to the ozone consumer with high efficiency.